Abrasive wheel and method of



Reissued Apr. 4, 1939 PATENT oi-rice- ABBASIVEWHEELANDMETHOD or ter, Masa,

, Baalis Sanford and Duane E. Webster, Worcesassignors to Norton Company,

Worcester, Mass.,- a corporation Massachu- No Drawing, Original No. 2,085,705, dated June -29;-19s7,' Serial No. 48,445, November 5, 1935. Application for reissue June.8,- 1938, Serial No.

The invention relatesto abrasivebodies, and with regardtd'its'fmore specific features, toifubberbonded grinding wheels' 4 one objectofthe invention isto' provide an improved "method of manufacturing a rubber bcnded'grin'ding'wheel or othr' abrasive Another object of the invention. is to provide a superior rubber bonded grinding wheel having 'moreuniform'grit size of abrasive particles, Another object of the invention is to provide a rubber bonded grinding wheel of large grit size of abrasive particles, and a practical method of m'akingthe same. Other objects'will be in part obviou s'or in part pointed out hereinafter." 1

The invention accordingly consists in 'the features-of construction; combinations ofelem'ents, arrangements of parts, and'in the several steps and relation and order of each of said steps team or more ofthe others thereof, all aswill be illustrativelydescribed herein, and'the scope oi.-the application of which will be indicated in the-following claims.

1 As conduciveto aclearer'understanding of the present ;invention it is noted. that fora long time the standard'way of making a rubber bonded grinding wheel has included the step of mixing the. abrasive grain with: the rubberon the. mill. Rubber in sheet-form, .upon which was thrown some sulphur, has been usually passed through between' steel'rollersseveral times, until somewhat plastic, being folded between passages to cause work to bedone on it, and then abrasive grain 'has-beemthrownonto it and it has been given :more and repeated passes between the' rolls.

Each-time .the rubberwould be folded, and the grain-would beadded little by little until the result was a plastic mass of rubber impregnated with abrasive grain. This working 'of the rubber, called milling, would continue for sometime involving, perhaps, upwards of one hundred passes between the rolls. The final result of this part of the process was a sheet of rubber with abrasive jgrains therein, which was of desired thickness and would he died out to form a grinding wheel in the green state, which when vulcanized would become a grinding wheel.

Such procedure has made a good grindingwheel for many purposes, but the great amount of mechanical work done on the rubber after.

the abrasive grain, or part thereof, was added has caused fracture of the individual, grains, so

dealing with large abrasive grit, the reduction of grain would be such that only a small proportionwould remain as'large sized grain. It may.

be desirable, 'for' example, for some purposes to produce an organicbonded wheel with grain of a large amount of grainvoi smaller size which,

for some purposes, might be undesirable.

' The" foregoing in part accounts for the popularity of synthetic" resinoid bonded wheels of recent years, for rubber has many excellent qualie ties and is reasonably inexpensive, and would 'fulflll most requirements were it not for the factors above mentioned and similar ones.

Considering now the procedure according to the present invention, we take a quantity of sheet rubber; crepe, caoutchouc, ball rubber or the like and mlll it between-rollers until it is plastic. We add the desired quantity of sulphur to make a hardrubber, for example 20% or more of sulphurby weight. .When the rubber is milled sufficiently. so that itisplastic and the .sulphur is well distributed therein, we die out disks which inarea correspond to the grinding wheel to be manufactured.

Whilewide variations may be made in carrying out the process so far as the thickness and number. of disks are concerned, we will now give a preferredembodiment oLtheinvention. Assumin vthat it is desired to produce 8. l2". diam;- eter wheel 1" thick, we roll the sheet rubber to 1 thick and'die out of the order of 10 disks thereof. We provide asuitable mold i'or'subj'ecting'the disks to pressure. In the bottom of the mold we place one rubber disk. We then spread a weighed quantityof l2 grit s'ize abrasive grain one layer thick upon the rubber. This may be done withan ordinary straight edge spreader or otherwise. Wethen place another sheet of rubber on top of the grain and spread another layer of grain of-equal -weight, the same mesh size and also one layer thick. We proceed in that fashion'until all the rubber disks are in the mold, there being desirably no abrasive grain upon the top disk. We then place the top plate of the mold upon the top rubber disk and hot press to a given volume under a pressure of the order of several thousand pounds: to the square inch. As a modification of the invention, we may apply the abrasive grain to the sheet instead of to the disks. In order to cause the grain to adhere while handling, we may make the sheet sticky by rubbing over it a smal1 quantity of gasoline or other solvent. The'grain may be sprinkled .onto the sheet.

We now remove the mold, clamp it and place in an over and vulcanire to the desired temperature for therlno-setting the rubber. It is possible to duplicate results very closely indeed by following the above given method of manufacture. Furthermore, the grit size of the abrasive grain put into the wheel is exactly that which is in the manufactured wheel, quite contrary to wheels made by the prior method herein described. If every grain put into this wheel is 12 grit size, then substantially every abrasive grain in the finished wheel is 12 grit-size.

The mention of 12 grit abrasive grain is for illustration of certain advantages of the invention and in its broader aspects the invention is not limited to any particular size of abrasive grain. Five hundred mesh grit ,size and finer may be used, if desired, and grains larger than 12 grit size may be used, if desired, and any intermediate sire whatsoever. Furthermore, the invention is in no wiselimited to the particular abrasive material used, for example alumina, silicon carbide, diamonds, garnet, emery, boron carbide, other carbide grains, and any variety of quartz may be employed. The invention has particular advantage when carried out with diamond grain, otherwise known as bort, in so much as there is little danger of grain being lost in the process of manufacture. It. will be appreciated that according to the prior methodherein described an extreme- 1y valuable abrasive grain would not beused because the method inevitably results in waste and loss of abrasive grain, at least as'heretofore carried out in practice,

In the application of pressure to the several rubber disks with abrasive grain therebetween, the grain' is forced into the rubber and a uniform structure of the wheel results. It is preferable to have the thickness of the sheets and the size of abrasive grain bear some relationship to each other, as indicated by the foregoing example. The exact relationship will depend upon the structure desired with respect to percentage bond content. Withinthaelimitsitisdesiredtomakethe sheets as thick as possible relative to the abrasive grains in order to coat every part of the grains with some bond.

It will thus be seen that there has been provided by this invention a method and an article in which the various objects hereinabove set forth together with many thoroughly practical advantages are-successfully achieved. As various possible embodiments might be made of the mechanicalfeatures of the above invention and as the artherein described, might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbeiore set forth is to be interv preted as illustrative and not in a limiting sense.

We claim 1. Method of making rubber bonded abrasive bodies which comprises forming rubber into a sprinkling on a quantity of abrasive grain, dieing out shapes from the sheet, introducing the shapes with the abrasive grains thereon into a mold, pressing the shapes. thus pressing the abrasive grain into them, and vulcanizing the pressed body resulting therefrom.

3.v Method oi making rubber bonded abrasive bodies which comprises taking a quantity of rubber and a vulcanizing agent, treating the rubber to make it so plastic that it can be readily mixed with abrasive grain, rolling the rubber with the vulcanizing agent into sheet form, dieing out shapes from the sheet, placing the sheets in a mold, introducing abrasive grain upon the sheets as they are placed in the mold, applying pressure, and vulcanizing.

4. Method of making rubber bonded abrasive bodies which comprises-taking aquantity of rubber and a vulcanizing agent, applying energy to the rubber and the vulcanizing agent together to make them so plastic that they can be readily mixed with abrasive grain, forming the mixture into sheet form, dieing out shapes from the sheet, covering each sheet with abrasive grain.

pressing the sheets together and vulcanizing.

5. Method of making rubber bonded abrasive bodies which comprises taking a quantity of rubber and a vulcanizing agent, applying energy to them to make them so plastic that they can be readily mixed with abrasive grain, forming the mixture into sheet form, dieing out shapes from the sheet, covering each shape with abrasive grain one layer thick, pressing the shapes together, and vulcanizing. 6. The method of making an abrasive wheel comprising placing alternate layers of fusible bonding material in the form of thin sheets and thin layers of loose abrasive in a mold cavity to the depth required to produce a wheel of the desired thickness and simultaneously heating suiflciently to soften the bonding material and compressing the thus assembled mass to agglomerate the mass and bond the same into a unitary structure.

seams SANEORD. DUANE a. wsss'rsa. 

